interface User{
    name: string
    age: number
    say: () => void
}

const u: User = {
    name: "小花",
    age: 18,
    say: () => {
        console.log("Hello");
    }
}

interface Fun{
    (x: number, y: number): number
}

const f:Fun = (x, y) => {
    return x + y
}